Encoder and motor device

Abstract

An encoder includes a rotary disc, a magnetic detection mechanism, an optical detection mechanism, a first detection signal generator, a second detection signal generator, and a multiple turn detector. The magnetic detection mechanism is to magnetically detect rotation of the rotary disc. The optical detection mechanism is to optically detect the rotation of the rotary disc. The first detection signal generator is configured to generate a first detection signal based on an output from the magnetic detection mechanism. The second detection signal generator is configured to generate a second detection signal having a predetermined phase difference from the first detection signal based on an output from the optical detection mechanism. The multiple turn detector is configured to detect a multiple turning amount of the rotary disc based on the first and second detection signals.

What is claimed is: 
     
         1 . An encoder comprising:
 a rotary disc;   a magnetic detection mechanism to magnetically detect rotation of the rotary disc;   an optical detection mechanism to optically detect the rotation of the rotary disc;   a first detection signal generator configured to generate a first detection signal based on an output from the magnetic detection mechanism;   a second detection signal generator configured to generate a second detection signal having a predetermined phase difference from the first detection signal based on an output from the optical detection mechanism; and   a multiple turn detector configured to detect a multiple turning amount of the rotary disc based on the first and second detection signals.   
     
     
         2 . The encoder of  claim 1 , further comprising:
 an illumination controller to control a light emitting element of the optical detection mechanism,   wherein the illumination controller controls the light emitting element to emit light for a predetermined period of time from a timing at which a level of the first detection signal changes, if a power source for the encoder is switched to a backup power source, and   wherein the illumination controller controls the light emitting element to stop emitting light after the predetermined period of time is elapsed.   
     
     
         3 . The encoder of  claim 1 ,
 wherein the magnetic detection mechanism includes
 a magnet rotatable together with the rotary disc, and 
 a magnetic detector configured to detect a magnetic field, and 
   wherein the first detection signal generator includes
 a fixed resistor, and 
 a hysteresis comparator configured to compare an output voltage of the magnetic detector with an output voltage of the fixed resistor to generate the first detection signal. 
   
     
     
         4 . The encoder of  claim 3 ,
 wherein a direction of a magnetic flux of the magnet reverses for every rotational angle range of substantially 180° at reversing positions,   wherein the reversing positions correspond to a home position of the rotary disc, and   wherein the first detection signal generator is configured to generate the first detection signal having one pulse per rotation of the rotary disc based on the output from the magnetic detection mechanism.   
     
     
         5 . The encoder of  claim 4 ,
 wherein the optical detection mechanism includes
 a light emitting element to emit light to the rotary disc, 
 an arc-shaped slit provided continuously in the rotary disc throughout a rotational angle range of substantially 180°, and 
 a photoreceiving element to receive light that is emitted from the light emitting element and that is affected by the arc-shaped slit, 
   wherein the second detection signal generator is configured to generate the second detection signal having one pulse per rotation of the rotary disc based on an output from the photoreceiving element.   
     
     
         6 . The encoder of  claim 5 , further comprising:
 an absolute position signal generator configured to generate an absolute position signal indicating an absolute position of the rotary disc within one rotation,   wherein the optical detection mechanism includes
 a slit array having an absolute pattern and provided in the rotary disc, and 
 a photoreceiving array to receive light that is emitted from the light emitting element and that is affected by the slit array, 
   wherein the absolute position signal generator is configured to generate the absolute position signal indicating the absolute position of the rotary disc within one rotation based on the output from the photoreceiving array.   
     
     
         7 . The encoder of  claim 6 ,
 wherein the light emitting element comprises a point light source,   wherein the arc-shaped slit is provided to reflect light emitted from the light emitting element to the photoreceiving element, and   wherein the slit array is provided to reflect light emitted from the light emitting element to the photoreceiving array.   
     
     
         8 . The encoder of  claim 5 , wherein the arc-shaped slit comprises an arc-shaped reflective groove to reflect light emitted from the light emitting element to the photoreceiving element. 
     
     
         9 . A motor device comprising:
 a motor to rotate a shaft; and   an encoder configured to detect a rotational position of the shaft, the encoder comprising:
 a rotary disc coupled to the shaft; 
 a magnetic detection mechanism to magnetically detect rotation of the rotary disc; 
 an optical detection mechanism to optically detect the rotation of the rotary disc; 
 a first detection signal generator configured to generate a first detection signal based on an output from the magnetic detection mechanism; 
 a second detection signal generator configured to generate a second detection signal having a predetermined phase difference from the first detection signal based on an output from the optical detection mechanism; and 
 a multiple turn detector configured to detect a multiple turning amount of the rotary disc based on the first and second detection signals.